MTD 122-250 User Manual download pdf (Page 2)

This document is !licensed under a Creative Commons Attribution 3.0 License: http://creativecommons.org/licenses/by-nc-sa/3.0/

instruction-count bounds. If so, instructions are added to their appropriate traces; and breakpoints and watchpoints are

monitored. If not, execution proceeds as in fast mode (but at less than a third of the speed).

2.2: TEST MODES

The test mode specifies which kind of program is to be run:

• In boot mode the KDF9 reads a 9-word bootstrap routine from TR0, then jumps to word 0, in Director state.

• In problem program mode ee9 reads into core, from TR0, a binary program prepared by a compiler (such as

David Holdsworth’s new Usercode compiler). Its execution starts at word 0, in program state. The emulator

itself services any OUTs executed by the program, so that it is not necessary to have a Director running.

• In test program mode ee9 reads a binary program into core from TR0, just as in problem program mode. Its

execution starts at word 0, but in Director state. The emulator services any OUTs executed by the program.

2.3: BREAKPOINTS, FETCHPOINTS , AND STOREPOINTS

Certain addresses in core can be marked as breakpoints or as watchpoints, to force diagnostic interaction with the user. A

breakpoint is set on an instruction word, and causes interaction after an instruction beginning in that word has been

executed. A fetchpoint is set on a data word, and causes interaction after data has been fetched from that word. A

storepoint is set on a data word, and causes interaction after data has been stored into that word. A watchpoint is both a

fetchpoint and a storepoint on the same word.

2.4: AUTHENTIC TIMING MODE

At option, ee9 can be made to insert timed pauses into its execution so that the elapsed time of a program run by ee9

approximates the elapsed time of a run on the KDF9 hardware. This may be instructive for younger users, who have

never seen characters being output by a computer, one at a time, and with noticeable delays! This mode can be set using

the authenticity option setting, see under ‘A’ in §5, or by means of the command-line visibility parameter.

3: INPUTS AND OUTPUTS

3.1: EMULATED KDF9 I/O DEVICES

At the start of a run ee9 casts around for files to represent the virtual KDF9 peripherals. If no file can be found for a

peripheral, it may be reported to be ‘offline’. There are fixed assignments for the console Flexowriter, which is associated

with the user’s interactive terminal window; for paper tape reader 0, which is associated with the standard input; and for

paper tape punch 0, which is associated with the standard output.

Other devices are associated with files having names derived from the device type. Magnetic tape deck d, for

example, is always associated with the file named ‘MTd’. It will often be convenient to have file system links of these

names, which may be redirected for each run of the emulator to the actual data files to be processed on that occasion. The

full list of these associations is as follows:

• card punches are ‘CPd’

• card readers are ‘CRd’

• drum stores are ‘DRd’

• fixed disc stores are ‘FDd’

• line printers are ‘LPd’

• KDF9 magnetic tape decks are ‘MTd’

• IBM seven-track tape decks are ‘STd’

• paper tape punches are ‘TPd’

• paper tape readers are ‘TRd’

3.2: THE FLEXOWRITER CONSOLE TYPEWRITER

The terminal window is the means by which users, in their rôle as KDF9 operators, can mimic Flexowriter I/O. The

Flexowriter is used to type-in responses to prompts output by problem programs or by Director. Repeatedly typing these

responses quickly becomes tedious. If a file named FW0 exists, it is used as a source of “canned” responses. They are

defined, with their identifying prompts, in FW0; and are picked up automatically by ee9. If a prompt spreads over more

When a prompt is issued, ee9 scans FW0, down from the last match found. If it finds a new match, it injects the given

response into the Flexowriter input stream; but if it reaches the end of the file without finding a match, it returns control

of the Flexowriter to the user’s terminal window, so that a manual response can be given. If a prompt matches a line in

FW0 that specifies a null response string (c.f. the second ‘OUT;’ in the following example) then ee9 terminates the run.

For example, the Whetstone Algol compiler prompts ‘OUT;’ to which a typical reply is ‘N.|’. If the Algol program

compiles, it runs and prompts ‘STREAM;’ to which a typical reply is ‘30.|’; but if the compilation fails the compiler

loops back to its ‘OUT;’ prompt, where the user will normally want to terminate the run so that the Algol source code can

be amended. The following data in FW0 will achieve this without user intervention:

OUT;N.|

STREAM;30.|

1 2 3 4 5 6 7 ... 14 15

Comments to this Manuals

No comments

MTD 122-250 User Manual Page 2

Comments to this Manuals

Related products and manuals for Lawnmowers MTD 122-250